The present invention relates generally to systems and methods for imitating the optical state of the atmosphere and more particularly to an optical scintillation system for simulating optical atmospheric turbulence.
Evaluation techniques for optical receivers existing prior to this invention required both laboratory and field testing in order to correlate receivers to atmospheric scintillation effects. Substantial prior work on the statistical behavior of atmospheric scintillation has provided a substantial data base of probability densities and distributions and power spectral densities of spatial distribution patterns of laser and non-laser sources for a variety of sources, atmospheric conditions and regional locale. However, testing of optical receivers is often needed under specific scintillation conditions, suitable statistical control over which is not always possible. A reliable laboratory instrument capable of spatially modulating collimated lght to simulate atmospheric turbulence conditions was therefore needed. Prior attempts to simulate atmospheric scintillation using fluid tanks and thermal heating of air failed to produce a device providing reproducible results which are both wavelength independent and statistically programmable in real time.
The invention provides a system for performing the function just described and which offers real-time statistical and wavelength independent control over the spatial intensity modulation of light sources used for laboratory analysis of optical receivers and provides realistic simulation of effects of optical atmospheric turbulence on laser and non-laser sources in order to minimize or eliminate requirements for extensive field testing of optical receivers. Acoustic energy coupled to a bounded reflective membrane through an electro-mechanical transducer sets up nodal vibrational modes in the membrane, creating angular distortion areas which redistribute energy in the reflected beam. Collimated light reflected off the membrane surface is spatially modulated in a manner which simulates effects observed over long path propagation through the atmosphere.
It is therefore a principal object of the invention to provide an optical scintillation system for simulating optical atmospheric turbulence effects.
It is a further object of the invention to provide a system for statistical programmability of atmosphere turbulence effects.
It is yet another object of the invention to provide an optical scintillation system for simulating long path propagation of a light beam through the atmosphere.
These and other objects of the invention will become apparent as the detailed description of representative embodiments proceeds.